I draw a pencil line where I want the top of the forend to end up, and with a razor sharp 1/2"chisel with the grain, I pare the wood down 'til I can just see the line. Then 80 grit abrasive cloth glued to a 12" walnut board two inches wide. I check frequently looking lengthwise to ensure I'm not introducing sunken spots...the forend needs to be perfectly parallel with the bore.
But with 1/2" to go, I too would bandsaw off most of it. Lay masking tape along the barrel channel so the saw doesn't chip away the inside.